Electret Mic amplifier

Thread Starter

Ylli

Joined Nov 13, 2015
965
Can anyone suggest a circuit as to how I can add an amplifier to an electret mic without requiring a seperate power supply? I.E. convert the first circuit into the second? Pull up resistor, voltage, and coupling cap can not change.
Annotation 2020-07-14 114020.png
 

Thread Starter

Ylli

Joined Nov 13, 2015
965
Something like this?
or missed the question
That does not provide bias for the Electret mic. And no, I can't run a separate Vcc line.

As further info, I've got a Baofeng UV-5R. These are know for low audio levels (put the unit right up to your mouth and talk loud - if your nose is not touching the unit the audio will be insufficient). FIgured I'd go with an external mic/speaker, but reports are that this has the same problem. Would like to be able to go into the mic case and add an amplifier without having to add batteries to the mic.
 

peterdeco

Joined Oct 8, 2019
183
I made this a while back and works great for a chip recorder needing a 32mV input. But for the life of me, I don't see any way to power it and output the audio on the same wire.
 

Attachments

Thread Starter

Ylli

Joined Nov 13, 2015
965
The amplifier would get power from that 3.3v/3K source. Was thinking of something like this, but I am having trouble getting enough current to the mic element without loading down the amplifier section until there is no gain left. [edit: The +3.3 volt source should be shown inside the transceiver block]
Annotation 2020-07-14 134750.png
 

Attachments

Thread Starter

Ylli

Joined Nov 13, 2015
965
I made this a while back and works great for a chip recorder needing a 32mV input. But for the life of me, I don't see any way to power it and output the audio on the same wire.
I've only got 1 wire and ground coming out of the transceiver. This circuit would require a separate power source.
 

DickCappels

Joined Aug 21, 2008
6,454
If you had a dynamic microphone you could use a transformer, but with an electret mic you're going to need a voltage source.

We might figure out how to get power and audio on the same conductor. Can you get clean voltage that can be used to power the preamp?

Have you looked for a microphone with better sensitivity or a built-in preamp?
 

Thread Starter

Ylli

Joined Nov 13, 2015
965
Attached a schematic snippet. (I'm pretty sure the wiring on the external mic jack is not quite right) Looks like I might have a separate +3.3 volt source available through R71, depending on whether or not it is brought through the cable up to the hand held speaker/mic I ordered. (This will be the mfg recommended external speaker/mic). If I do have that +3.3 volts available at the mic, I might go as far as to try using a SSM2167. Should have the mic in a couple days.
Annotation 2020-07-15 115500.png
 
Last edited:
Top